Danger was lurking in the opinion of head coach Jim Harbaugh, who stopped practice Wednesday night at Levi's Stadium because of an unplayable field.

By Thursday, workers were ripping out portions of the sod and replacing it with new turf. The 49ers said the field will be ready for Sunday's preseason game against the San Diego Chargers.

Visible divots and chunks of sod, remnants of last Sunday's stadium-opening game in Santa Clara, Calif., against the Denver Broncos caused several players to slip, trip and hit the deck. Harbaugh stopped practice, and the 49ers sent home fans who'd come to the brand new stadium to see the team's final practice at the $1.3 billion facility.

Practice resumed on the team's typical practice fields but was closed to fans who received complimentary tickets and media.

"The 49ers organization would like to apologize to any fans who were inconvenienced by today's practice ending early," team spokesman Bob Lange said in a statement. "We have determined the appropriate measures necessary to have the field ready for Sunday and look forward to hosting the San Diego Chargers."

The stadium sod was laid in April.

After Sunday's preseason date with the Chargers, the 49ers do not play at home until Sept. 14, a "Sunday Night Football" game against the Chicago Bears.